1. Field of the Invention
The present invention relates to an apparatus and method for quickly locating a liver portal vein to establish a shunt through a human liver between the portal vein and the hepatic vein, and more particularly to a Transjugular Intrahepatic Portosystemic Shunt (“TIPS”) device and a method for establishing a TIPS using the device.
2. Description of Related Art
The human liver has many functions essential to life including breaking down fats, glucose metabolism/storage, urea production, amino acid synthesis, toxin filtration, storage of vitamins and minerals, and cholesterol metabolism. On average, the healthy liver receives around 70-75% of its blood supply from the portal vein and 25-30% from the hepatic artery. Blood leaves the liver through the hepatic veins which communicate with the inferior vena cava just below the heart.
Liver cirrhosis is a term that refers to irreparable damage to the liver where the hepatic parenchyma is progressively replaced with scar tissue. With time, this can progress to complete liver failure. There are numerous causes of liver cirrhosis, but common causes include alcohol abuse, hepatitis, non-alcoholic steatohepatitis (NASH), toxin/drug exposure, and various inherited and autoimmune conditions. As the liver becomes cirrhotic, the normal blood flow patterns become altered. Specifically, the pressure within the portal veins increases causing the blood that would normally flow to the liver to “back-up.” Over time the portal blood that normally flows towards the liver (hepatopedal) can reverse and flow away from the liver (hepatofugal). As the portal vein pressures rise, the blood finds alternative routes to return to the heart. This typically occurs in the form of variceal vessels that are particularly prone to hemorrhage with potentially fatal consequences.
In addition, the increased portal vein pressures observed with cirrhosis raises capillary hydrostatic pressures within the splanchnic vascular bed of the viscera. Coupled with impaired renal function and sodium retention, as the hydrostatic pressure rises, a transudative fluid collection, known as ascites, can form in the patient's abdomen. Although typically this is initially managed with medical therapy, the amount of fluid can become quite large and refractory to medical therapy.
Originally described by Rosch et al. in 1969, the TIPS procedure creates a shunt between the portal veins and the hepatic veins allowing blood to bypass the cirrhotic hepatic parenchyma that is responsible for the elevated portal vein pressures. In so doing, the TIPS procedure decreases portal pressure and is indicated in the management of variceal bleeding refractory to medical therapy, refractory ascites, and refractory hepatic hydrothorax (fluid surrounding the lungs secondary to liver failure).
There are several commercially available kits for the TIPS procedure. The TIPS procedure is performed under general anesthesia by accessing the patient's right internal jugular vein and advancing a catheter through the superior vena cava, heart, and inferior vena cava to the right hepatic vein. Once catheter access to the right hepatic vein is made, a larger sheath is then placed into the right hepatic vein. Through this sheath a large needle (typically 16 Gauge) is pushed through the wall of the hepatic vein into the parenchyma anteroinferomedially in the expected direction of the right portal vein. After the needle has been advanced, a syringe is attached to the back of the needle and the needle is slowly withdrawn. When blood is aspirated, a small injection of contrast is made into the needle to confirm access into the right portal vein. Wire access through the needle into the right portal vein and main portal vein is then made. Over this wire, a tract is balloon dilated and a covered stent is placed thus forming the shunt.
Despite the use of preprocedural imaging as well as intraprocedural wedge portography, access to the portal vein can often prove difficult requiring numerous passes of the needle before access is obtained. The passage of the needle through the liver is associated with complications including intraperitoneal bleeding (frequency 1-13%), hemobilia (frequency 1-4%), and fistula formation (frequency <1%). Equally important, the difficulty of portal vein access extends procedure time with the increased use of hospital resources/expenses and the added risk to the patient of prolonged anesthesia and fluoroscopic radiation exposure. Therefore, there is a need for a TIPS device and method that can obtain access to the portal vein more safely and rapidly.